1. Field of the Invention
The present invention relates generally to tumbler locks and more particularly to a tumbler lock having tamper preventing and indicating features.
2. Description of the Prior Art
It is well known that locks, particularly the tumbler locks of the less expensive variety such as pin tumbler, wafer tumbler and disc tumbler, can be defeated by the manipulation of a properly constructed pick inserted in the lock keyway. Various types of tamper preventing mechanisms, such as wards or milled or corrugated keyways have been proposed to make it more difficult for such locks to be successfully opened by means other than a properly coded key.
Inasmuch as prior art lock mechanisms have been unable to distinguish between authorized and unauthorized objects inserted in the lock keyway, there have heretofore been no satisfactory proposals for detecting a tamper attempt and providing a suitable response such as activating an alarm or inhibiting further lock movement. Furthermore, it has often been found desirable to provide such a response from the very instant the tamper attempt begins, rather than after the lock has been opened.